Databases Reference
In-Depth Information
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Original
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Approach 1
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Approach 2
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F I GU R E 11 . 4
Sinusoid and reconstructions.
^
^
x
n
d
n
d
n
d
n
Q
x
n
^
−
^
x
n
−1
^
x
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−1
Decoder
x
n
^
Delay
Encoder
F I GU R E 11 . 5
A simple differential encoding system.
^
^
x
n
+
d
n
d
n
d
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Q
x
n
^
-
+
p
n
p
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P
p
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Decoder
^
x
n
P
Encoder
F I GU R E 11 . 6
The basic algorithm.
This basic differential encoding system is known as the differential pulse code modulation
(DPCM) system. The DPCM system was developed at Bell Laboratories a few years after
World War II [
169
]. It is most popular as a speech-encoding system and is widely used in
telephone communications.
As we can see from Figure
11.6
, the DPCM system consists of two major components, the
predictor and the quantizer. The study of DPCM is basically the study of these two components.
